Remove unused use statements

Author: greg0ire

cache.rst

@@ -567,9 +567,6 @@ to enable this feature. This could be added by using the following configuration
     .. code-block:: php
 
         // config/packages/cache.php
-        use Symfony\Component\Cache\Adapter\ChainAdapter;
-        use Symfony\Component\DependencyInjection\Reference;
-
         $container->loadFromExtension('framework', [
             'cache' => [
                 'pools' => [

reference/configuration/swiftmailer.rst

@@ -381,7 +381,6 @@ alternatives based on the :ref:`service binding <services-binding>` feature:
         // config/services.php
         use App\Some\Service;
         use Psr\Log\LoggerInterface;
-        use Symfony\Component\DependencyInjection\Reference;
 
 
         $container->register(Service::class)